The driver told investigators he intended to turn left onto State Street, heading east, but instead turned left onto the railroad tracks.
The vehicle got stuck.
"It appears the fact that it was dark out, raining out, had something to do with his judgment," Zalewski said.
He said alcohol was not a factor in the incident. The driver could be facing a traffic citation for traveling onto the tracks.
Zalewski said the driver and the child were able to get out of the car and leave the immediate area once they spotted an approaching train.
"The officer on scene reported it was less than five minutes from the time the vehicle got stuck on the tracks to the time when the train actually struck it," Zalewski said. "So they had literally a matter of minutes to figure out what to do."
Zalewski said crashes between vehicles and trains are extremely rare in Wauwatosa. He said the only ones on record in the last six years were two vehicle vs. train crashes in 2014.
Zalewski added there was also an accident involving a train and a pedestrian, in which the pedestrian was killed, in 2012.
However, Zalewski said police are regularly called to vehicles reported stuck on the railroad tracks.
"It's not that this is the fist time this has happened," Zalewski said, "or that it's that unusual."
An official with Canadian Pacific Railway, who visited the scene on Wednesday afternoon, said he estimates roughly a dozen vehicles have ended up stuck on the tracks near 68th & State in the last year.
Zalewski said that number sounds accurate. He said drivers are typically able to call police, or the railroad company, and first responders stop any coming trains while a stuck vehicle is towed.
Zalewski said he's thankful Tuesday night's crash resulted in no injuries.
"Obviously, a train striking a vehicle, that's a devastating collision that occurs," he said.